Air Handling Units (AHUs) are widely used in with heating, ventilating, air conditioning, and refrigerating (HVACR) systems to control temperature and humidity in commercial spaces. Outdoor air usually accounts for the largest heat transfer load. The term “outdoor air” can refer to air from outside the room, or air from outside the building. Outdoor air generally imparts loads on these systems by entering through door openings and dedicated AHU outdoor air intake openings. Minimization of air infiltration without a sacrifice in air quality is a common goal of HVACR system design.
In the interest of reducing air infiltration issues, air entrances have been established that use high velocity air streams impinged on door openings at right angles to the flow direction of people or products through the door opening. These systems reduce air infiltration at the cost of added fan power and limitations on operational effectiveness due to the maximum velocity. Maximum velocity is dictated by what is comfortable to the customer or users of the interior space. Such air entrance doors have been used in buildings such as supermarkets for over 40 years. According to Boon Edam there are over 3,000 entrances considered air entrance doors around the world. Claimed benefits include reduced insect and rodent infiltration (claims as high as 50%); comfortable front end areas; an open feel to the building occupants; less dirt in the buildings; energy savings; and no automatic door law suits or maintenance for automatic doors. Detracting from these benefits are high capital costs; negligible energy savings and possibly an increase in energy consumption; annoying air blowing on customers' hair; cold drafts in the winter, warm drafts in the summer as customers walk through the entrance; maintenance problems of keeping a pit clean and an additional HVAC system to repair; and a large floor grille that some people are uncomfortable to walk on, approximately 5 feet across.